Stockholders' Equity (Repurchases of Common Stock Under Share Repurchase Programs) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Equity, Class of Treasury Stock [Line Items]      
Stock repurchased to satisfy tax withholding obligations, Mone $ 37 $ 36 $ 46
Stock repurchased to satisfy tax withholding obligations, Shares 0.7 0.7 0.8
Total stock repurchases, Monetary 862 1,286 1,496
Total stock repurchases, Shares 16.6 27.8 29.8
Share Repurchase Program [Member]
     
Equity, Class of Treasury Stock [Line Items]      
Stock repurchased under our stock repurchase programs, Monetary $ 825 $ 1,250 $ 1,450
Stock repurchased under our stock repurchase programs, Shares 15.9 27.1 29.0